The Q.931 protocol has been accepted as the standard for ISDN signaling channel communications over a central office loop to a subscriber location. In such an arrangement, a terminal at the subscriber's location generates user interface information (e.g., which features and buttons are used at the terminal) from call control information sent using the Q.931 protocol. Each terminal requires a relatively powerful processor, a collection of special sophisticated algorithms, a large random-access-memory (RAM) and a large read-only-memory (ROM) to generate the user interface information. Additionally, this call control complexity increases proportionally with the number of line buttons on a station terminal. Unfortunately, these additional capabilities add significantly to the cost of station terminals. Moreover, to upgrade or add a feature to the terminals may require that changes be made to each terminal which adds significant terminal upgrade costs; since changes to the administrative data must be performed on a per terminal basis thereat.
What is desirable is a way to reduce terminal production cost and customer upgrade cost of the terminals while maintaining their compatibility with the Q.931 protocol standard.